NBB.Core.Pipeline

NBB.Core.Pipeline

A multi-purpose pipeline builder

NuGet install

dotnet add package NBB.Core.Pipeline

Philosophy

A pipeline is a function of some context, composed from one or multiple middleware. Each middleware receives the context and the next middleware, and is responsible of how and when to invoke the next middleware.

Design pattern

Chain of Responsibility is a behavioral design pattern that lets you pass requests along a chain of handlers. Upon receiving a request, each handler decides either to process the request or to pass it to the next handler in the chain.

Pipeline middleware

Create the middleware class by implementing the IPipelineMiddleware interface:

private class SomeMiddleware : IPipelineMiddleware<IContext>
{
    public async Task Invoke(IContext ctx, CancellationToken cancellationToken, Func<Task> next)
    {
        ctx.Log.Add("FirstBefore");
        await next();
        ctx.Log.Add("FirstAfter");
    }
}

Now register the middleware with the pipeline:

//somewhere in a func
var pipeline = new PipelineBuilder<IContext>()
    .UseMiddleware<SomeMiddleware, IContext>()
    .UseMiddleware<SomeOtherMiddleware, IContext>()
    .Pipeline;

Functional pipeline middleware

If you don't require constructor injection you can model the middleware using just a function.

var pipeline = new PipelineBuilder<IContext>()
    .Use(async (ctx, cancellationToken, next) =>
    {
        ctx.Log.Add("FirstBefore");
        await next();
        Thread.Sleep(100);
        ctx.Log.Add("FirstAfter");
    })
    .Use(async (data, cancellationToken, next) =>
    {
        ctx.Log.Add("SecondBefore");
        await next();
        ctx.Log.Add("SecondAfter");
    })
    .Pipeline;

Pipeline context

You can use whatever context type for your pipeline, the only restriction is to expose an instance of the IServiceProvider

public interface IPipelineContext
{
    IServiceProvider Services { get; }
}

public record MessagingContext
    (MessagingEnvelope MessagingEnvelope, string TopicName, IServiceProvider Services) : IPipelineContext;

Pipeline execution

The PipelineBuilder.Pipeline returns just a function, that when executed executes the pipeline

var pipeline = new PipelineBuilder<SomeContext>()
    .UseMiddleware<FirstMiddleware, SomeContext>()
    .Pipeline;

await pipeline(new SomeContext(), default);